Compression Spring Calculator

Inputs

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Diameter of the spring wire.
mm
Center-to-center across the coil (outside diameter − wire diameter).
mm
Coils that actually deflect (total coils minus the end coils).
Unloaded overall length — used for solid height and the buckling check.
mm
Working compression — used for force and stress at that point.
mm
Sets the shear modulus G and the allowable shear stress.
Sets the inactive end coils and the buckling end-fixity assumption.

Results

Default result
Edit inputs
Spring rate(k)
1.239N/mm

Also computed

Spring index(C)Pass10

Solid height10mm

Approx. body pitch(p)4.75mm

Approximate open-body pitch at free length.

d + travel-to-solid / active coils; verify against the drawing.

Wahl factor(Kᵥᵥ)1.145

Corrected shear stress(τ)Pass361.2MPa

Within allowable.

Allowable shear stress995MPa

Static limit at this wire size.

Force vs DeflectionThe load line uses the computed spring rate up to travel-to-solid; the operating marker is clamped at the available travel.Force vs Deflection0102030400102030operatingDeflection (mm)Force (N)
The load line uses the computed spring rate up to travel-to-solid; the operating marker is clamped at the available travel.
Method notes 3 notes
  • Static load; ignores fatigue, set and stress relaxation.
  • Allowable shear stress is the static torsional limit at this wire size (45% of estimated tensile strength), before set removal.
  • Buckling assumes the ends are seated between parallel flat surfaces.

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